1. Field of the Invention
This invention relates to a method for processing and applying pavement materials. In particular, it relates to the use of naturally occurring bituminous sandstone in pavement surfaces.
2. Discussion of the Prior Art
Pavement surfaces, by their very nature, are subject to continuous wear by their users, i.e., by the constant travel of pedestrians, automobiles and aircraft. Pavement surfaces are also subject to degradation because they are exposed to the elements, i.e., rain, snow and extreme temperatures. As a result, pavement surfaces are repeatedly damaged by the formation of cracks, potholes, and the like. Consequently, there is a great need for materials to repair such damage simply and inexpensively.
One method for repairing pavement surfaces is known as "hot patch" repair. Hot patch repair employs a tar-like material which is heated to approximately 400.degree. F. and then immediately forced into or over damaged areas. A major drawback of hot patch materials and methods is that they require relatively expensive equipment to heat the tar-like material on-site. Further, the method generally requires that the damaged pavement be pretreated with a preliminary coating of a base material to provide sufficient bonding between the material and the damaged area.
Another method of repair is described in U.S. Pat. No 4,859,502 to Astrope et al., which patent is hereby incorporated by reference. The method employs mixing bituminous sandstone with heated water in a ratio of 20 to 56% water, by weight, to form a slurry having a temperature of from 110.degree.-210.degree. F. The temperature of the slurry is maintained within this range throughout the mixing process in order to maintain its properties. The slurry is then pumped through a conduit and applied to the area to be repaired. Among the disadvantages of the method disclosed in the Astrope et al. patent is the cost of the equipment needed to form the hot slurry and then pump the material to the damaged area.
Attempts have also been made to use bituminous sandstone in paving and repair operations which are "cold", i.e., performed without heating. In central Utah, where large deposits of bituminous sandstone exist, roads are constructed using this material in a dry state. When road damage occurs, additional bituminous sandstone is used to repair the holes, again in a dry state, without special processing or treatment. Unfortunately, the naturally occurring material is difficult to work with because it is mined in aggregate chunks which are difficult to reduce to a uniform grain size. The material is also extremely difficult to transport in the dry state because it solidifies in the course of transportation into a large mass which cannot be handled efficiently. Accordingly, untreated bituminous sandstone material is not useful in most paving operations.